Reactivity with rabbit immunoglobulin G of cold agglutinins isolated from group C streptococcal antisera.

Cold agglutinin antibodies were isolated from group C streptococcal antisera by thermal elution from rabbit erythrocytes. These antibodies reacted with bovine submaxillary mucin, fetuin, immunoglobulin G, and the Fc fragment of immunoglobulin G in hemolytic inhibition assays. Further, in radioimmunoassay these antibodies reacted with the major glycopeptide fragment of rabbit immunoglobulin G. Affinity-purified group carbohydrate-specific antibodies reacted weakly with glycopeptide. These data suggest that certain populations of antibody in group C streptococcal antisera may participate in tissue reactivity via interaction with cell surface glycoproteins, including immunoglobulin G.